Gaseous air pollution and emergency hospital visits for hypertension in Beijing, China: A time-stratified case-crossover study

Background. A number of epidemiological studies have been conducted to research the adverse effects of air pollution on mortality and morbidity. Hypertension is the most important risk factor for cardiovascular mortality. However, few previous studies have examined the relationship between gaseous air pollution and morbidity for hypertension. Methods. Daily data on emergency hospital visits (EHVs) for hypertension were collected from the Peking University Third Hospital. Daily data on gaseous air pollutants (sulfur dioxide (SO₂) and nitrogen dioxide (NO₂)) and particulate matter less than 10 m in aerodynamic diameter (PM₁₀) were collected from the Beijing Municipal Environmental Monitoring Center. A time-stratified case-crossover design was conducted to evaluate the relationship between urban gaseous air pollution and EHVs for hypertension. Temperature and relative humidity were controlled for. Results. In the single air pollutant models, a 10 g/m³ increase in SO₂ and NO₂ were significantly associated with EHVs for hypertension. The odds ratios (ORs) were 1.037 (95% confidence interval (CI): 1.004-1.071) for SO₂ at lag 0 day, and 1.101 (95% CI: 1.038-1.168) for NO₂ at lag 3 day. After controlling for PM₁₀, the ORs associated with SO₂ and NO₂ were 1.025 (95% CI: 0.987-1.065) and 1.114 (95% CI: 1.037-1.195), respectively. Conclusion. Elevated urban gaseous air pollution was associated with increased EHVs for hypertension in Beijing, China.